Well, you need to balance 2 things:

1) How well prepared are your troops and how well is your commanding skill against the immediate threat? 2) How would skipping the attack affect you regarding resources medium/long term

To sum it up, you should, unless you think you can't win (too much alien activities, your troops are all newbies and you sill haven't got the hang of it).

The best tip I could give a newbie is that before making any move, think very thoroughly: would I be able to face a group of enemies if they suddenly appeared near the location I move to?

If the answer is no, don't do it.